Method for the fabrication of stiffening corrugations in thin-walled, hard sheets, especially of circumferential crease

ABSTRACT

Method of production of beads in thin-walled hard sheet, especially of circumferential creases in rotors of centrifuges, by means of a roller and a counter roller as the pressing tools which accomodate between them the material to be worked; the method includes pressing a roof-shaped groove into the hard material within its limits of plastic deformation and then superimposing on the roller an oscillatory motion at right angles to the groove for broadening the groove at right angles to its direction of extension.

United States Patent Zippe 1 June 6, 1972 54] METHOD FOR THE FABRICATION 0F [56] References Cited UNITED STATES PATEN S 1,844,469 2/1932 Giesler 61 3| ..72/105 CREASE FOREIGN PATENTS OR APPLICATIONS Gernot Zippe, Julich, Germany Gesellschaft fur Kernverfahrenstechnik mbH, Julich, Germany Mar. 3, 1970 Inventor:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Mar. 3, i969 Austria ..A 2073/69 US. Cl ..72/84, 72/105, 72/182 ..B2ld 17/04 Field of Search ..72/105, 106, 181, 182, 74, 72/84, 85; 29/454 867,034 6/l94l France ..72/l 8l Primary Examiner-Lowell A. Larson AtmrneySpencer & Kaye [57] ABSTRACT Method of production of beads in thin-walled hard sheet. especially of circumferential creases in rotors of centrifuges. by means of a roller and a counter roller as the pressing tools which accomodate between them the material to be worked; the method includes pressing a roof-shaped groove into the hard material within its limits of plastic deformation and then superimposing on the roller an oscillatory motion at right an- 1 gles to the groove for broadening the groove at right angles to its direction of extension.

3 Claims, 5 Drawing Figures PATENTEDJuu 6 m2 SHEET 10F 2 Figjd Fig. 1c

FigJb INVENTOR. Gernoi Zippe way ,2 BY

ATTORNEYS.

PATENTEDJUH BIS"? 3687.265

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INVENTOR. Gernor Zippe METHOD FOR FABRICATION OF STIFFENING CORRUGATIONS IN THIN-WALLED, HARD SHEETS, ESPECIALLY F CIRCUMFEREN'IIAL CREASE The invention relates to a method for the production of beads in thin-walled hard sheet, especially of circumferential creases in rotors of centrifuges, by means of rollers and counter rollers as the forming tools accomodating between them the material to be worked.

For centrifuges, especially gas ultracentrifuges, equipped with rotors operated overcritically it has been suggested before to subdivide the cylindrical wall of the rotor into several longitudinal sections by means of elastic intermediates. These intermediates, which may be shaped like circumferential creases or beads, should be as rigid as possible relative to transverse displacements of the longitudinal axes of the two consecutive rotor sections and they should be relatively flexible with respect to angular deformations about the rotor axis. Since centrifugal rotors of this type are made mostly of very high-strength material of low ductility, the familiar methods of impressing creases of this kind, e.g., hydraulic forming, raise certain difficulties because the material hardens too quickly and must be softened again, which requires expensive intermediate steps.

Hence, the present invention serves the purpose of creating a method for the production of creases or beads which permits the fabrication of these elastic intermediates at relatively simple expense and with accurately defined properties even in very hard, thin-walled materials. This is based on the familiar method of pressure rolling by means of rollers and counter rollers between which the material is passed.

The solution of the problem to which the invention is directed includes pressing a roof-shaped groove into the material within its limits of plastic deformation, which groove then is broadened at right angles to its direction of extension. For broadening, an oscillatory motion is superimposed on the rotary motion of the roller, at right angles to the groove. For forming out, it is useful to have the first roller followed by a second roller of the same effective forming height, but with a greater width.

Depending upon the desired depth of the creases, these methods are continued in several steps with different pairs of rollers in each case, depending upon the desired ultimate shape of the crease.

The method according to the invention makes it possible to produce the desired creases wholly or partly in hardened material, in which case care must be taken not to exceed the residual plastic yield point when impressing the roof-shaped groove. Although this may require a larger number of steps and roller shapes in some cases compared with the forming of unhardened material, it makes for a considerable increase in strength as a result of cold working, which is desirable especially for centrifuge rotors.

Further details of the invention are explained by way of examples on the basis of the drawings:-

FIGS. 1a, 1b, 1c, and 1d are schematic representations of the steps of the process with different pairs of rollers in each case.

FIG. 2 is a schematic representation of a multi-press rolling device for the production of circumferential creases in tubes.

Rollers 1 and 2 of FIG. 1a are pivoted around their axes 3, 4

and accomodate between their outer surfaces 5, 6 the wall of the tube 7 to be worked. Counter roller 2 has a depression 8 which is broader than its counterpart rim 9 of roller 1. Roller l is movable perpendicular to its axis of rotation 3 so that it is possible initially to press a roof-shaped circumferential groove 10 into the tube 7 by means of the rim 9. In this step, the rim 9 acts roughly on the middle of the depression 8. For subsequent groove broadening, roller 1 is moved back and forth under pressure parallel to its axis of rotation 3. This oscillatory motion is indicated by the two arrows on either side of roller 1 in the right half of FIG. 1a.

In FIG. lb, after broadening, the groove'lOb is formed out by a roller 11 whose pressing rim 12 is broader than that of roller 1 in FIG. 1a.

FIGS. 1c and 1 d show the further steps of the process,

which are identical in principle, in which depressions l3 and 14, respectively, of the counter rollers 15 and 16 are made deeper and, at the same time, narrower than depression 8 to attain the desired ultimate shape of the grooves and 10d, respectively, while the pressing rims 17 and 18, respectively, of the pressing rollers 19 and 20d have a correspondily larger effective height.

The press rolling device according to FIG. 2 consists essentially of a rotary drive mechanism 20, 21, 22 for rotating the pressing rollers 23, 24. Rollers 23 and 24 are supported and braced by means of hollow shaft 21 and set bolt 22 which, in turn, are coupled with a rotary drive 20. In addition, the hollow shaft and set bolt are supported by track supporting rollers 27 at their free ends. The pressing rollers 23, 24 can be moved perpendicular and also parallel to their axis by a pressing device (not shown) so that circumferential creases 29 are produced in the tube 28 to be worked.

The supporting and bracing device 21, 22 permits easy exchange of the rollers for the individual process steps. In order to save sets of rollers, it is possible to build the rollers out of several single disks which, depending upon the number of disks, permit e.g., a variation of the effective widths of the counter roller depression and pressing roller rim.

The invention is not limited to the example described. Thus, it can be employed under the same principle e.g., to press beads along tube surface lines or into plane sheet.

I claim:

1. Method of production of beads in thin-walled hard sheet, especially of circumferential creases in rotors of centrifuges, by means of a roller and a counter roller as the pressing tools which accomodate between them the material to be worked, comprising the steps of pressing a roof-shaped groove into the material within its limits of plastic deformation and then superimposing on the roller an oscillatory motion at right angles to the groove for broadening said groove at right angles to its direction of extension.

2. Method as claimed in claim 1, further comprising, after broadening, following the roller with a second roller the pressing rim of which is broader than that of the first roller for forming out the groove.

3. Method as claimed in claim 1, further comprising further steps for producing the ultimate shape of the bead, where every consecutive step uses counter rollers with increasingly larger depression depths and increasingly narrower depression widths and pressing rollers having pressing rims becoming correspondingly higher and narrower. 

1. Method of production of beads in thin-walled hard sheet, especially of circumferential creases in rotors of centrifuges, by means of a roller and a counter roller as the pressing tools which accomodate between them the material to be worked, comprising the steps of pressing a roof-shaped groove into the material within its limits of plastic deformation and then superimposing on the roller an oscillatory motion at right angles to the groove for broadening said groove at right angles to its direction of extension.
 2. Method as claimed in claim 1, further comprising, after broadening, following the roller with a second roller the pressing rim of which is broader than that of the first roller for forming out the groove.
 3. Method as claimed in claim 1, further comprising further steps for producing the ultimate shape of the bead, where every consecutive step uses counter rollers with increasingly larger depression depths and increasingly narrower depression widths and pressing rollers having pressing rims becoming correspondingly higher and narrower. 